1. Technical Field
Embodiments of the present disclosure relate to object detection, and more particularly to a non-destructive detection method for detecting a state of a solder ball.
2. Description of Related Art
During manufacture of electronic products, a circuit device and a printed circuit board are often connected therein using solder balls. FIG. 1 is a partial cross section showing an upper board 100 and a lower board 200 connected by a solder ball 10. For example, the upper board 100 can be one side surface of the circuit device and the lower board 200 can be the printed circuit board. An upper contacting portion 150 is positioned between the upper board 100 and the solder ball 10. A lower contacting portion 450 is positioned between the lower board 200 and the solder ball 10. The manufacturing process sometimes makes an incomplete solder ball 10 including a solder void 50 and a crack 60.
Common techniques for detecting the solder void 50 and crack 60 includes two methods. One method is a red ink detection method and the other method is an X-ray tomography method. In the red ink detection method, the solder ball 10 is immersed into a red ink and a mechanical force separates a detected portion of the solder ball 10. Then, a microscope is used to observe a penetration situation of the red ink of the detected portion of the solder ball 10. However the red ink detection method is a destructive method and the immersed solder ball 10 cannot be detected repeatedly.
FIG. 2 is a horizontal scanography image detected by an X-ray machine of FIG. 1. The solder ball 10 is shown as a circular line. The upper contacting portion 150 and the lower contacting portion 450 are shown as two circular dotted lines. In the X-ray tomography method, the solder void 50 and the crack 60 are detected by an X-ray machine. If a thickness of material of the solder ball 10 is increased, an X-ray absorption of the material of the solder ball 10 is increased. As shown in FIG. 2, the solder void 50 is detected as the circular dotted line in the horizontal scanography image detected by an X-ray machine. However, the crack 60 may be too small that the X-ray machine cannot detect them.